Transparent sound absorbing panels

ABSTRACT

A sound absorbing panel and method therefor comprising providing a first sheet of photosensitive material, applying a first mask having a first plurality of features to the first sheet of photosensitive material, exposing the masked material to ultraviolet light, heating the first sheet of photosensitive material to form crystals in exposed portions of the first sheet, and etching the crystals to form a second plurality of features in the first sheet of photosensitive material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §119 ofU.S. Provisional Application Ser. No. 61/968135 filed on Mar. 20, 2014the content of which is relied upon and incorporated herein by referencein its entirety.

BACKGROUND

In various types of indoor or outdoor environments, such as offices,reception or production halls, healthcare facilities and hospitals,sports halls and swimming pools, classrooms, and the like, it can bedesirable and statutorily regulated, to provide acoustic conditions tothe environment. Acoustic conditions can be described by reverberation,and to control this, sound absorbing elements are conventionally used,such as sound absorbing panels attached to walls, ceilings, and othersurfaces.

Sound absorbing panels as surfaces for attachment to indoor walls andceilings can use various physical effects for the absorption of sound.Some conventional sound absorbing panels include fiber-based absorbentscomprising porous panels of mineral fibers (rock and glass wool) thatact to dampen sound as the sound waves penetrate into the panel. Theseconventional panels reduce the energy of the sound waves by viscouslosses in pores or structures of the panel. Some conventional soundabsorbing panels include structures based on the Helmholz resonatorprinciple. Such panels generally include slits or apertures as well asfiber fabric (with or without mats) or porous fiber materials behind thepanel to obtain satisfactory absorption.

Such conventional sound absorbing panels provide several disadvantages.For example, upon damage or wear such conventional panels can producefibers to the environment. As these fibers are often made of meltedglass or rock, any airborne fibers can irritate the respiratory passagesof persons in the surrounding environment. Additionally, these fiberscan limit the appearance of such panels as it can be difficult to keepthem clean as they require minimum use of moisture when cleaning, andproblems related to mold can arise in exterior paneling or locationsexposed to moisture (e.g., swimming pools or the like).

Microperforated panels can obviate the disadvantages of conventionalfiber panels; however, conventional microperforated panels and foils areproduced by rolling a tool having a plurality of many small spikes overthe surface of the panel. Other methods of producing microperforatedpanels, such as laser cutting and plastic moulding, are used for thickerpanels but are not commercially viable for certain substrate materials,and certain hole depths and/or distributions.

Thus, there is a need in the industry to provide transparent soundabsorbing panels capable of being utilized in interior and exteriorenvironments without the disadvantages of conventional paneling. Thereis also a need for new sound absorbing panels that provide a clean andsmooth surface that can be easily manufactured.

SUMMARY

The disclosure generally relates to the sound absorbing panels usingglass, glass ceramics, or other material for exterior and interiorenvironments. Exemplary materials can be in some embodimentsphotosensitive. Thus, in some embodiments the photosensitive materialscan be masked and patterned to form micro-perforations which act todampen sound waves.

In some embodiments a method of making a sound absorbing panel isprovided. The method can include providing a first sheet ofphotosensitive material, applying a first mask having a first pluralityof features to the first sheet of photosensitive material, and exposingthe masked material to ultraviolet light. The method also includesheating the first sheet of photosensitive material to form crystals inexposed portions of the first sheet and etching the crystals to form asecond plurality of features in the first sheet of photosensitivematerial.

In other embodiments a sound absorbing panel is provided having a firstsheet of photosensitive material and a resilient surface spaced apartfrom the first sheet of photosensitive material by a predetermineddistance. The sheet of photosensitive material includes a firstplurality of features etched therein, and the dimensions anddistribution of the first plurality of features and the predetermineddistance are determined as a function of sound aborptive characteristicsof the panel.

In further embodiments, a sound absorbing panel is provided comprising afirst sheet of photosensitive material and a resilient surface spacedapart from the first sheet of photosensitive material by a predetermineddistance. The first sheet of photosensitive material can include aplurality of features formed therein without mechanical etching (i.e.,formed by chemical etching or other means not including mechanicaletching).

Additional features and advantages of the claimed subject matter will beset forth in the detailed description which follows, and in part will bereadily apparent to those skilled in the art from that description orrecognized by practicing the claimed subject matter as described herein,including the detailed description which follows, the claims, as well asthe appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description of various embodiments of the presentdisclosure, are intended to provide an overview or framework forunderstanding the nature and character of the claimed subject matter.The accompanying drawings are included to provide a furtherunderstanding of the present disclosure, and are incorporated into andconstitute a part of this specification. The drawings illustrate variousembodiments and together with the description serve to explain theprinciples, operations, and variations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

These figures are provided for the purposes of illustration, it beingunderstood that the embodiments disclosed and discussed herein are notlimited to the arrangements and instrumentalities shown.

FIG. 1 is a block diagram of a method according to some embodiments.

FIGS. 2A and 2B are depictions of exemplary microperforated panelstructures according to some embodiments and equivalent circuits.

FIG. 3A is an illustration of hole and etch variations according to someembodiments.

FIG. 3B is an illustration of non-limiting mask designs according tosome embodiments.

FIGS. 4A and 4B are photographs of a microperforated sample according tosome embodiments.

FIG. 5 is a series of plots illustrating acoustic absorption of someembodiments.

FIG. 6 is a plot of measured acoustic absorption between someembodiments, conventional glass and one inch foam.

FIGS. 7A and 7B are plots comparing experimental measurements of twoembodiments with theoretical models.

FIG. 8 is a plot comparing measurements of acoustic absorption ofadditional embodiments as a function of perforation ratio.

FIG. 9 is a plot comparing measurements of acoustic absorption offurther embodiments as a function of cavity depth.

While this description can include specifics for the purpose ofillustration and understanding, these should not be construed aslimitations on the scope, but rather as descriptions of features thatcan be including in and/or illustrative for particular embodiments.

DETAILED DESCRIPTION

Various embodiments for transparent sound absorbing panels are describedwith reference to the figures, where like elements have been given likenumerical designations to facilitate an understanding of the presentdisclosure.

In the following description, like reference characters designate likeor corresponding parts throughout the several views shown in thefigures. It also is understood that, unless otherwise specified, termssuch as “top,” “bottom,” “outward,” “inward,” and the like are words ofconvenience and are not to be construed as limiting terms. In addition,whenever a group is described as comprising at least one of a group ofelements and combinations thereof, the group can comprise, consistessentially of, or consist of any number of those elements recited,either individually or in combination with each other.

Similarly, whenever a group is described as consisting of at least oneof a group of elements or combinations thereof, the group can consist ofany number of those elements recited, either individually or incombination with each other. Unless otherwise specified, a range ofvalues, when recited, includes both the upper and lower limits of therange. As used herein, the indefinite articles “a,” and “an,” and thecorresponding definite article “the” mean “at least one” or “one ormore,” unless otherwise specified

Those skilled in the art will recognize that many changes can be made tothe embodiments described while still obtaining the beneficial resultsof the invention. It also will be apparent that some of the desiredbenefits of the present disclosure can be obtained by selecting some ofthe described features without using other features. Accordingly, thoseof ordinary skill in the art will recognize that many modifications andadaptations are possible and can even be desirable in certaincircumstances and are part of the invention. Thus, the followingdescription is provided as illustrative of the principles of the presentdisclosure and not in limitation thereof.

Those skilled in the art will appreciate that many modifications to theexemplary embodiments described herein are possible without departingfrom the spirit and scope of the invention. Thus, the description is notintended and should not be construed to be limited to the examples givenbut should be granted the full breadth of protection afforded by theappended claims and equivalents thereto. In addition, it is possible touse some of the features of the present disclosure without thecorresponding use of other features. Accordingly, the foregoingdescription of exemplary or illustrative embodiments is provided for thepurpose of illustrating the principles of the present disclosure and notin limitation thereof and can include modification thereto andpermutations thereof.

Embodiments of the present disclosure are generally directed to soundabsorbing panels using photosensitive materials. Exemplary panels can becomprised of photosensitive glass or glass-ceramics (among othermaterials) and during the process of manufacture can be masked, exposedto ultraviolet (UV) radiation, and patterned to form sound absorbingfeatures which can include micro-perforations, features or holes, whichact to dampen sound wavefronts. It should be noted that the terms soundabsorbing feature, perforation, feature, hole, channel and the pluralforms thereof are utilized interchangeably in this disclosure; such useshould not limit the scope of the claims appended herewith. Exemplary,non-limiting photosensitive materials can include a glass material orglass ceramic material having a main crystal phase comprising lithiumdisilicate Li₂Si₂O₅. FIG. 1 is a block diagram of a method according tosome embodiments. With reference to FIG. 1, a base photosensitive glassor glass-ceramic can be melted and cast into a monolithic product, e.g.,glass or glass-ceramic sheet, or thin film in step 10. In some examples,base photosensitive glasses and glass-ceramic materials can be derivedfrom the SiO₂—Li₂O system. In some embodiments, the base photosensitiveglass or glass-ceramic material can be produced in the form of a verythin film or sheet of a specific thickness (e.g., in the range fromabout 20 μm to about 2 mm) In additional embodiments, the sheet or filmcan be strengthened by various methods, including chemical strengthening(e.g., by ion-exchanging methods), thermally strengthened (e.g., bytempering or annealing) or otherwise strengthened to provide additionalstrength, scratch resistance or other suitable characteristics to anexemplary panel or structure. In some embodiments, the basephotosensitive glass or glass-ceramic material can contain Ce³⁺- andAg⁺-ions. Exemplary compositions include between about 75-85 wt % SiO₂,about 2-6 wt % Al₂O₃, about 7-11 wt % Li₂O, about 3-6 wt % K₂O, about0.5-2.5 wt % Na₂O, about 0.01-0.5 wt % Ag, about 0.01-0.5 wt % Sb₂O₃,about 0.01-0.04 wt % CeO₂, about 0-0.01 wt % Au, and about 0-0.01 wt %SnO₂. In one embodiment, a composition can include about 79.6 wt % SiO₂,about 4.0 wt % Al₂O₃, about 9.3 wt % Li₂O, about 4.1 wt % K₂O, about 1.6wt % Na₂O, about 0.11 wt % Ag, about 0.4 wt % Sb₂O₃, about 0.014 wt %CeO₂, about 0.001 wt % Au, and about 0.003 wt % SnO₂. Of course, thesephotosensitive compositions are exemplary only and should not limit thescope of the claims appended herewith as other photosensitive glass andglass ceramic compositions can be utilized.

The thin sheet or product can then be exposed to UV light using a maskat step 12. During exposure to UV light, photoelectrons can cause theoxidation of Ce³⁺ to Ce⁴⁻ in an exemplary composition, and as a result,Ag⁺ can be reduced to Ag⁰ using the following relationship: Ce^(3|)+h·ν(312 nm)→Ce^(4|)+e⁻; Ag^(|)+e⁻→Ag⁰. This metal colloid (e.g., metallicsilver) can be the nucleating agent for a lithium metasilicate Li₂SiO₃phase. As a result, this crystal phase can be precipitated by controlledcrystallization at high temperatures, e.g., approximately 600° C. Thus,in some embodiments, the UV exposed product can be heat treated andlithium metasilicate crystals Li₂SiO₃ subsequently precipitatedtherefrom at step 14. The Li₂SiO₃ can then be etched at step 16. In someembodiments, the lithium metasilicate crystals can be etched with dilutehydrofluoric acid (HF) or another suitable etchant. Other etchantsinclude, but are not limited to, potassium hydroxide, isopropyl alcohol,EDP (ethylenediamine pyrocatechol), tetramethylammonium hydroxide,phosphoric acid, acetic acid, nitric acid, hydrochloric acid, hydrogenperoxide, citric acid, sulfuric acid, ammonium fluoride, ceric ammoniumnitrate, water, and combinations thereof. Of course, the type of etchantutilized in exemplary embodiments can be determined by the underlyingsubstrate or material to be etched. In such a manner, defined structuresor patterns can be easily etched into a finished product including soundabsorbing features. In further embodiments, UV exposure and heattreatment can be conducted again at step 18 whereby approximately 40 wt% of the main crystal phase lithium disilicate can be produced alongwith a-quartz with a total crystal content of approximately 60%. Throughsuch exemplary UV and masking techniques as well as subsequent etchingstep(s), embodiments according to the present disclosure can producesmaller and more intricate sound absorbing features (e.g., perforations,holes, channels, or the like), e.g., on the order of about 20 to 50 μm.

In additional embodiments, the sound absorbing features can have a depthand/or diameter of 20 μm, 40 μm, 60 μm, 100 μm, 0.1 mm, 0.3 mm 0.5 mm,1.0 mm, 1.5 mm, 2.0 mm, etc., and can perforate through the entirethickness of the plate. In additional embodiments, holes or features ina plate can have varying depths or diameters, that is, each hole orfeature in a plate can have a depth different or substantially the sameas adjacent holes or features. FIG. 3A is an illustration of hole andetch variations according to some embodiments. With reference to FIG.3A, holes or features according to some embodiments can having varyingdiameters through the depth of the hole or feature 32, 34 can terminatebefore perforating the panel 33, can vary between adjacent holes in apattern 35, can be angled through the depth of the hole or feature 36,can be conical in shape (or other geometry) 37, or can form a throat 38.Such small, intricate features are difficult to produce using mechanicalor laser machining processes especially for high volume productionpurposes requiring a high perforation ratio for large area coverage.

Exemplary embodiments can thus provide a smaller hole or perforationsize to enable a thinner overall sound absorbing structure by reducingthe cavity depth required for achieving high sound absorption. Thisadvantage can save space in interior and exterior designs. For example,an exemplary acoustic dampening panel can employ friction by viscousairflow to dampen sound waves. This panel can comprisemicroperforations, e.g., holes through a panel (or portions thereof)whereby the holes have a diameter of less than 0.5 mm. A conventionalmicroperforated panel (MPP) box (including the enclosed cavity) may beas wide as 100 mm; however, with the smaller perforation featuresenabled by the disclosed embodiments, e.g., on the order of about 20 to50 μm, the required cavity depth between the panel and rear surface canbe significantly reduced to about 10 to 20 mm thereby reducing the spacerequired for acoustic dampening in architectural or other applications.Furthermore, such exemplary panels are not dependent on fiber materials.Applications of such sound absorbing panels include, but are not limitedto, sound isolation of car engines, sound absorbing elements inbuildings, interior or exterior spaces, among others.

FIG. 2A is an exemplary microperforated panel (MPP) structure accordingto some embodiments and an equivalent circuit. With reference to FIG.2A, an exemplary microperforated structure 20 includes a panel 21 havinga thickness (t) and microperforations or holes 22 each with a diameter(d) and a spacing (b) therebetween. The holes 22 can be arranged at adistance or cavity depth (D) from a rear surface 23 with the perforatedpanel 21 facing a sound source P. Exemplary structures 20 and/or panels21 can be formed from materials such as, but not limited to, sheetmetal, plastic, plywood, acrylic, glass, glass ceramic, etc. The soundabsorbing property of an exemplary MPP structure 20 can be determined byparameters thereof and properties of air. For example, the impedance ofan MPP, z=r−iωm, is given by the following equations:

$\begin{matrix}{r = {\frac{32\; \eta}{p\; \rho \; c}\frac{t}{d^{2}}\left( {\sqrt{1 + \frac{x^{2}}{32}} + {\frac{\sqrt{2}}{32} \times \frac{d}{t}}} \right)}} & (1) \\{{{\omega \; m} = {\frac{\omega \; t}{pc}\left( {1 + \frac{1}{\sqrt{1 + \frac{x^{2}}{2}}} + {0.85\frac{d}{t}}} \right)}}{where}} & (2) \\{x = {\frac{d}{2}\sqrt{\frac{\rho \; \omega}{\eta}}}} & (3)\end{matrix}$

and d, p, t represent the hole diameter, perforation ratio and thickness(e.g., throat length) of an MPP, respectively, h represents thecoefficient of viscosity, r represents air density, c represents thespeed of sound, and ω represents the angular frequency of sound, whereω=2 pf.

Some embodiments can include a single MPP and a rigid-back wall orsubstrate with an air cavity in-between (cavity depth of D) as depictedin FIG. 2A (left and center) which can then be modeled by an equivalentelectrical circuit (FIG. 2A right). A series of Helmholtz resonators canthus be formed by the holes and the cavity. Other embodiments caninclude a second (or additional) panel(s) 25 to provide a double-leafMPP absorber with a rigid-back wall to broaden the absorption range. Inone non-limiting embodiment, two resonators can be formed as depicted inFIG. 2B (left) with its equivalent electrical circuit depicted in FIG.2B (right).

It has also been discovered that the porosity or perforation ratio σ canbe related to hole diameter (d) and spacing (b) using the followingrelationship:

$\begin{matrix}{\sigma = \frac{\pi \cdot d^{2}}{4 \cdot b^{2}}} & (4)\end{matrix}$

It is known that conventional glass and glass ceramic materials have asound absorption coefficient (α) close to zero. This can lead to anexcessively long reverberation time (RT) resulting in a loss of speechintelligibility and acoustic discomfort if too much glass is used in theplanar or curved surfaces of a room, hall, etc. Using Sabine's formularelating sound absorption α to RT₆₀, the time required for reflectionsof a direct sound to decay 60 dB can be determined using the followingrelationship:

$\begin{matrix}{{RT}_{60} = {0.161\frac{V}{\sum\limits_{i}{\alpha_{i} \cdot S_{i}}}}} & (5)\end{matrix}$

where V represents the volume of room or space, and α_(i) and S_(i)represent the sound absorption coefficient of a surface and the surfacearea, respectively.

By utilizing embodiments of the present disclosure described herein, anexemplary glass, glass ceramic or other material surface can be madeinto a highly acoustic-absorptive apparatus. The acoustic absorption (α)of an exemplary MPP (having a thickness (t), holes with diameter (d),cavity depth (D) and spacing (b) therebetween, see, e.g., FIGS. 2A-2B)structure can thus be modeled and described using Equations (1)-(3) andthe relationship:

$\begin{matrix}{\alpha = \frac{4r}{\left( {1 + r} \right)^{2} + \left( {{\omega \; m} - {\cot \left( {\omega \; {D/c}} \right)}} \right)^{2}}} & (6)\end{matrix}$

While FIG. 2A-2B illustrate a symmetrical pattern of cylindrical holes22, the claims appended herewith should not be so limited as the shape,size, distribution, number, configuration, etc. of holes or features canbe a function of mask design and/or the application of the respectiveMPP structure. FIG. 3B provides exemplary, non-limiting mask designs 30a, 30 b, 30 c, 30 d where different size, shape, distribution of themicro-holes can be designed to suit functional and/or aestheticrequirements of a user. With reference to FIG. 3B, a mask design caninclude cylindrical holes each having a substantially similar diameterand symmetrically arranged by row and column 30 a, cylindrical holeseach having a substantially similar diameter and arranged by row andoffset by column 30 b, star-shaped holes each having similar dimensionsand arranged by row and offset by column 30 c, star-burst forms havingdissimilar dimensions and asymmetrically arranged 30 d, etc. Of course,these mask designs and subsequent hole or feature arrangements areexemplary only and should not limit the scope of the claims appendedherewith as the size, shape and distribution of the holes can befunctionally or aesthetically suitable to the acoustic and/or aestheticrequirements of a user. Thus, any arbitrary shapes or combination ofdifferent shapes of the micro-features and arbitrary distributions ofsuch features in a surface can be possible and are envisioned. Suchintricate features as shown in FIGS. 3A and 3B can be convenientlytranslated to a photosensitive glass, glass ceramic, or other materialplate via the UV exposure process, followed by an exemplary chemicaletching process as described above.

FIGS. 4A and 4B are photographs of a microperforated sample according tosome embodiments. With reference to FIG. 4A, a disk-shapedmicroperforated sample 40 is illustrated having a plurality of sets 42of cylindrical holes or features symmetrically arranged by row andcolumn. FIG. 4B is a microscopic view of the features 44 in a setillustrated in FIG. 4A. The material employed was a photosensitivematerial having a composition include between about 75-85 wt % SiO₂,about 2-6 wt % Al₂O₃, about 7-11 wt % Li₂O, about 3-6 wt % K₂O, about0.5-2.5 wt % Na₂O, about 0.01-0.5 wt % Ag, about 0.01-0.5 wt % Sb₂O₃,about 0.01-0.04 wt % CeO₂, about 0-0.01 wt % Au, and about 0-0.01 wt %SnO₂. The microperforated sample 40 included through holes 44 having adiameter of about 100 μm and a spacing between adjacent holes of about200 μm.

The MPP structure depicted in FIGS. 4A and 4B was then tested using anacoustic impedance tube for sound absorption measurement. FIG. 5 is aseries of plots illustrating acoustic absorption of some embodiments.With reference to FIG. 5, the experimental results for cavity depths (D)of 5 mm, 45 mm, 105 mm and 145 mm were measured utilizing the MPPstructure of FIGS. 4A and 4B and are graphically illustrated. As isreadily observed, each embodiment provides noticeable improvements toacoustic absorption over that of a glass sheet 52.

FIG. 6 is a plot of measured acoustic absorption between someembodiments, conventional glass and one inch foam. With reference toFIG. 6, the acoustic absorption of an exemplary MPP structure 62 havinga distance d between adjacent holes of 135 μm, plate thickness t about0.66 mm, and a cavity depth D of 5 mm, an exemplary MPP structure 64having a distance d between adjacent holes of 135 μm, plate thickness tabout 0.66 mm, and a cavity depth D of 25 mm were measured and comparedwith the acoustic absorption of a one inch foam core 66 and a sheet ofconventional glass 68. It was observed that conventional glass has verylow absorption, while both exemplary MPP structures provide a broadbandand comparable absorption as the foam core.

FIGS. 7A and 7B are plots comparing experimental measurements of twoembodiments with theoretical models. With reference to FIG. 7A, acousticabsorption of an exemplary MPP structure 72 having a cavity depth D of10 mm, plate thickness t about 1.3 mm and an exemplary MPP structure 74having a cavity depth D of 35 mm and plate thickness t about 1.3 mm werecompared with the model-predicted acoustic absorption of the samestructures 73, 75, respectively. It can be observed that the measuredand model-predicted acoustic absorption of the two different MPPstructures were in agreement. With reference to FIG. 7B, acousticabsorption of an exemplary MPP structure 76 having a cavity depth D of25 mm, plate thickness t about 0.66 mm and an exemplary MPP structure 78having a cavity depth D of 5 mm and plate thickness t about 0.66 mm werecompared with the model-predicted acoustic absorption of the samestructures 77, 79, respectively. It can again be observed that themeasured and model-predicted acoustic absorption of the two differentMPP structures were in agreement.

FIG. 8 is a plot comparing measurements of acoustic absorption ofadditional embodiments as a function of perforation ratio. Withreference to FIG. 8, acoustic absorption of exemplary MPP structureshaving a hole diameter of 0.25 mm and fixed cavity depth D of 2 mm weremeasured from a 0.25% perforation ratio 82, to a 0.5% perforation ratio84, a 1% perforation ratio 86, a 2.5% perforation ratio 87, and a 5%perforation ratio 88. As illustrated in FIG. 8, an impact of increasingperforation ratio from 0.25% to 5% on sound absorption of a MPPstructure can be markedly observed.

FIG. 9 is a plot comparing measurements of acoustic absorption offurther embodiments as a function of cavity depth. With reference toFIG. 9, acoustic absorption of exemplary MPP structures having a holediameter of 50 μm and a fixed perforation ratio of 10% were measuredwith a cavity depth D of 2 mm 92, a cavity depth D of 4 mm 94, a cavitydepth D of 6 mm 96, a cavity depth D of 8 mm 97, and a cavity depth D of10 mm 98. As illustrated in FIG. 9, an impact of increasing cavity depthfrom 2 mm to 10 mm for a fixed diameter 50 μm hole can be markedlyobserved. Thus, it follows that embodiments described herein can beoptimally designed for the application required, e.g., acousticabsorption requirements vs. optical transparency and/or visual impact ofthe hole patterns based on a multi-variable (d, b or a, t, D) designapproach.

Some embodiments can thus be employed to dissipate or convert acousticalenergy into heat. In these embodiments, sound waves propagate into anexemplary panel and because of the proximity of the panel to a rearsurface, oscillating air molecules inside the structure lose theiracoustical energy due to friction between the air in motion and thesurface of the MPP. Additional embodiments can also be tuned by holegeometry and distribution, as well as the air gap (cavity depth) behindthe panel as described above. Thus, by varying geometrical and materialparameters, the acoustical performance of some embodiments can betailored to meet a multitude of specifications in various applications.

Exemplary embodiments can thus provide a pristine, smooth and hardsurface of glass that is highly desirable in architectural and interiordesign and can be sound absorbing. Embodiments can be transparent forlighting, durable, scratch and soil resistant and can be aestheticallyappealing while having low sound absorption—a characteristic which isuncommon in a material (e.g., glass) known for its intrinsic near-zerosound absorption and large excessive reverberation time (RT).Conventional glass finds limited use in enclosed spaces such asclassrooms, offices, conference rooms, patient wards and elevator cabinsdue to such large RT; however, exemplary embodiments as described hereincan be employed to balance acoustics and provide the aesthetic appealrequested by architects, designers, and residents alike.

While embodiments have been described as including photosensitive glass,the claims appended herewith should not be so limited as it isenvisioned that transparent, substantially transparent, opaque, and/orcolored acrylics, glass-ceramics, and polymers can be employed as anexemplary panel and are suitable with the described processes.Furthermore, while some embodiments have been described as having flatpanel shapes and specific distributions (e.g., holes in certainpatterns), the claims appended herewith should not be so limited asembodiments can be flat or curved (e.g., three dimensional) and can haveslits, ridges, channels or other patterns (symmetrical or asymmetrical)depending on the type or types of mask(s) employed. Thus, embodimentscan eliminate the need for mechanical or laser drilling processcurrently used in making sound absorbers and can be shaped in threedimensions to suit any respective design and application needs.

Embodiments described herein can also employ a photosensitive substratematerial and can be formed with a mask design having micro-features orpatterns that can produce the required or desired acoustic absorption ina microperforated panel structure. Exemplary embodiments made ofphotosensitive glass, glass ceramics or other materials can be furtherdecorated using printing technology to add further design appeals.Different native colors of the panel are also possible through heattreatment and material composition design.

In some embodiments a method of making a sound absorbing panel isprovided. The method can include providing a first sheet ofphotosensitive material, applying a first mask having a first pluralityof features to the first sheet of photosensitive material, and exposingthe masked material to ultraviolet light. In some embodiments, the stepof providing a first sheet of photosensitive material can include thesteps of melting the glass and casing the molten glass into thin sheet.The method also includes heating the first sheet of photosensitivematerial to form crystals in exposed portions of the first sheet andetching the crystals to form a second plurality of features in the firstsheet of photosensitive material. In a further embodiment this methodcan include repeating these steps for a second sheet of photosensitivematerial. In further embodiments, a resilient surface spaced apart fromand substantially in the same shape of the first or second sheet ofphotosensitive material can be provided wherein the first and secondsheets of photosensitive material are between the resilient surface andenvironment. In some embodiments, the second plurality of features issubstantially similar to the first plurality of features. In anotherembodiment, the method includes applying a second mask having a thirdplurality of features to the etched first sheet of photosensitivematerial, exposing the masked material to ultraviolet light, heating thefirst sheet of photosensitive material to form crystals in exposedportions of the first sheet, and etching the crystals to form a fourthplurality of features in the first sheet of photosensitive material. Insome embodiments, the fourth plurality of features is substantiallysimilar to the first plurality of features. The sheets of materialsdescribed herein can be planar or three dimensional. In someembodiments, the method can include bending the first sheet ofphotosensitive material before the step of applying the mask or afterthe step of etching the crystals. Exemplary photosensitive material canbe, but are not limited to, a glass or glass ceramic material. In someembodiments, the first sheet photosensitive material can comprise about75-85 wt % SiO₂, about 2-6 wt % Al₂O₃, about 7-11 wt % Li₂O, about 3-6wt % K₂O, about 0.5-2.5 wt % Na₂O, about 0.01-0.5 wt % Ag, about0.01-0.5 wt % Sb₂O₃, about 0.01-0.04 wt % CeO₂, about 0-0.01 wt % Au,and about 0-0.01 wt % SnO₂. In a further embodiment, the method caninclude tinting, coloring or decorating the first sheet ofphotosensitive material. The sheets of photosensitive material can alsobe strengthened if necessary. The features provided in the sheet canhave a diameter or depth of up to about 20 μm, up to about 40 μm, up toabout 60 μm, up to about 100 μm, up to about 0.1 mm, up to about 0.3 mm,up to about 0.5 mm, up to about 1.0 mm, up to about 1.5 mm, or up toabout 2.0 mm.

In other embodiments a sound absorbing panel is provided having a firstsheet of photosensitive material and a resilient surface spaced apartfrom the first sheet of photosensitive material by a predetermineddistance. The sheet of photosensitive material includes a firstplurality of features etched therein, and the dimensions anddistribution of the first plurality of features and the predetermineddistance are determined as a function of sound aborptive characteristicsof the panel. In some embodiments, the etched features can be formed byapplying a mask having the plurality of features therein to the firstsheet of photosensitive material, exposing the masked material toultraviolet light, heating the material glass to form crystals in theexposed glass, and etching the crystals to form the plurality offeatures in the first sheet of material. In other embodiments, the firstsheet of material is three dimensional. Exemplary photosensitivematerial can be, but are not limited to, a glass or glass ceramicmaterial. In some embodiments, the first sheet photosensitive materialcan comprise about 75-85 wt % SiO₂, about 2-6 wt % Al₂O₃, about 7-11 wt% Li₂O, about 3-6 wt % K₂O, about 0.5-2.5 wt % Na₂O, about 0.01-0.5 wt %Ag, about 0.01-0.5 wt % Sb₂O₃, about 0.01-0.04 wt % CeO₂, about 0-0.01wt % Au, and about 0-0.01 wt % SnO₂. Exemplary thicknesses of the sheetscan be, but are not limited to, up to about 20 μm, up to about 40 μm, upto about 60 μm, up to about 100 μm, up to about 0.1 mm, up to about 0.3mm, up to about 0.5 mm, up to about 1.0 mm, up to about 1.5 mm, or up toabout 2.0 mm. The photosenstive material can be translucent,transparent, tinted, colored, or decorated and can also be strengthened.The features provided in the sheet can have a diameter or depth of up toabout 20 μm, up to about 40 μm, up to about 60 μm, up to about 100 μm,up to about 0.1 mm, up to about 0.3 mm, up to about 0.5 mm, up to about1.0 mm, up to about 1.5 mm, or up to about 2.0 mm. In anotherembodiment, the panel includes a second sheet of photosensitive materialhaving a second plurality of features etched therein, the second sheetintermediate the first sheet and the resilient surface.

In further embodiments, a sound absorbing panel is provided comprising afirst sheet of photosensitive material and a resilient surface spacedapart from the first sheet of photosensitive material by a predetermineddistance. The first sheet of photosensitive material can include aplurality of features formed therein without mechanical etching. In someembodiments, the etched features can be formed by applying a mask havingthe plurality of features therein to the first sheet of photosensitivematerial, exposing the masked material to ultraviolet light, heating thematerial glass to form crystals in the exposed glass, and etching thecrystals to form the plurality of features in the first sheet ofmaterial. In other embodiments, the first sheet of material is threedimensional. Exemplary photosensitive material can be, but are notlimited to, a glass or glass ceramic material. In some embodiments, thefirst sheet photosensitive material can comprise about 75-85 wt % SiO₂,about 2-6 wt % Al₂O₃, about 7-11 wt % Li₂O, about 3-6 wt % K₂O, about0.5-2.5 wt % Na₂O, about 0.01-0.5 wt % Ag, about 0.01-0.5 wt % Sb₂O₃,about 0.01-0.04 wt % CeO₂, about 0-0.01 wt % Au, and about 0-0.01 wt %SnO₂. Exemplary thicknesses of the sheets can be, but are not limitedto, up to about 20 μm, up to about 40 μm, up to about 60 μm, up to about100 μm, up to about 0.1 mm, up to about 0.3 mm, up to about 0.5 mm, upto about 1.0 mm, up to about 1.5 mm, or up to about 2.0 mm. Thephotosenstive material can be translucent, transparent, tinted, colored,or decorated and can also be strengthened or, specifically, chemicallystrengthened or thermally strengthened. The features provided in thesheet can have a diameter or depth of up to about 20 μm, up to about 40μm, up to about 60 μm, up to about 100 μm, up to about 0.1 mm, up toabout 0.3 mm, up to about 0.5 mm, up to about 1.0 mm, up to about 1.5mm, or up to about 2.0 mm. In another embodiment, the panel includes asecond sheet of photosensitive material having a second plurality offeatures etched therein, the second sheet intermediate the first sheetand the resilient surface.

While this description can include many specifics, these should not beconstrued as limitations on the scope thereof, but rather asdescriptions of features that can be specific to particular embodiments.Certain features that have been heretofore described in the context ofseparate embodiments can also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination. Moreover,although features can be described above as acting in certaincombinations and can even be initially claimed as such, one or morefeatures from a claimed combination can in some cases be excised fromthe combination, and the claimed combination can be directed to asubcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings or figures in aparticular order, this should not be understood as requiring that suchoperations be performed in the particular order shown or in sequentialorder, or that all illustrated operations be performed, to achievedesirable results. In certain circumstances, multitasking and parallelprocessing can be advantageous.

As shown by the various configurations and embodiments illustrated inFIGS. 1-9, various embodiments for transparent sound absorbing panelshave been described.

While preferred embodiments of the present disclosure have beendescribed, it is to be understood that the embodiments described areillustrative only and that the scope of the invention is to be definedsolely by the appended claims when accorded a full range of equivalence,many variations and modifications naturally occurring to those of skillin the art from a perusal hereof.

What is claimed is:
 1. A method of making a sound absorbing panelcomprising the steps of: a) applying a first mask having a firstplurality of features to a first sheet of photosensitive material toform a masked material; b) exposing the masked material to ultravioletlight; c) heating the first sheet of photosensitive material to formcrystals in exposed portions of the first sheet; and d) etching thecrystals to form a second plurality of features in the first sheet ofphotosensitive material.
 2. The method of claim 1 further comprising thestep of repeating steps a) through d) for a second sheet ofphotosensitive material.
 3. The method of claim 2 further comprising thestep of providing a resilient surface spaced apart from andsubstantially in the same shape of the first or second sheet ofphotosensitive material wherein the first and second sheets ofphotosensitive material are between the resilient surface andenvironment.
 4. The method of claim 1 further comprising the steps of:a) applying a second mask having a third plurality of features to theetched first sheet of photosensitive material; b) exposing the maskedmaterial to ultraviolet light; c) heating the first sheet ofphotosensitive material to form crystals in exposed portions of thefirst sheet; and d) etching the crystals to form a fourth plurality offeatures in the first sheet of photosensitive material.
 5. The method ofclaim 1, wherein the first sheet of material is three dimensional. 6.The method of claim 1 further comprising either one or both the step oftinting, coloring or decorating the first sheet of photosensitivematerial and the step of strengthening the first sheet photosensitivematerial.
 7. The method of claim 1, wherein the second plurality offeatures have a diameter or depth of up to about 20 μm, up to about 40μm, up to about 60 μm, up to about 100 μm, up to about 0.1 mm, up toabout 0.3 mm, up to about 0.5 mm, up to about 1.0 mm, up to about 1.5mm, or up to about 2.0 mm.
 8. A sound absorbing panel comprising: afirst sheet of photosensitive material; and a resilient surface spacedapart from the first sheet of photosensitive material by a predetermineddistance, wherein the sheet of photosensitive material includes a firstplurality of features.
 9. The sound absorbing panel of claim 8, whereinthe first plurality of features comprise etched features.
 10. The soundabsorbing panel of claim 8, wherein the first sheet of material is threedimensional.
 11. The sound absorbing panel of claim 8, wherein thephotosensitive material is a glass or glass ceramic material.
 12. Thesound absorbing panel of claim 8, wherein the photosensitive materialcomprises: about 75-85 wt % SiO₂, about 2-6 wt % Al₂O₃, about 7-11 wt %Li₂O, about 3-6 wt % K₂O, about 0.5-2.5 wt % Na₂O, about 0.01-0.5 wt %Ag, about 0.01-0.5 wt % Sb₂O₃, about 0.01-0.04 wt % CeO₂, about 0-0.01wt % Au, and about 0-0.01 wt % SnO₂.
 13. The sound absorbing panel ofclaim 8, wherein the first sheet has a thickness of up to about 20 μm,up to about 40 μm, up to about 60 μm, up to about 100 μm, up to about0.1 mm, up to about 0.3 mm, up to about 0.5 mm, up to about 1.0 mm, upto about 1.5 mm, or up to about 2.0 mm.
 14. The sound absorbing panel ofclaim 8, wherein the photosensitive material is translucent,transparent, tinted, colored, or decorated.
 15. The sound absorbingpanel of claim 8, wherein the photosensitive material is strengthened.16. The sound absorbing panel of claim 8, wherein the features have adiameter or depth of up to about 20 μm, up to about 40 μm, up to about60 μm, up to about 100 μm, up to about 0.1 mm, up to about 0.3 mm, up toabout 0.5 mm, up to about 1.0 mm, up to about 1.5 mm, or up to about 2.0mm
 17. The sound absorbing panel of claim 8 further comprising a secondsheet of photosensitive material having a second plurality of featuresetched therein, the second sheet intermediate the first sheet and theresilient surface.
 18. A sound absorbing panel comprising: a first sheetof photosensitive material; and a resilient surface spaced apart fromthe first sheet of photosensitive material by a predetermined distance,wherein the first sheet of photosensitive material includes a pluralityof features formed therein without mechanical etching.
 19. The soundabsorbing panel of claim 18 wherein the plurality of features are formedby chemical etching.
 20. The sound absorbing panel of claim 18, whereinthe first sheet of material is three dimensional.